Foam encased pump

ABSTRACT

A compact pump has a uni-body, or alternately a two-part, housing of self-skinning foam construction for superior noise and vibration reduction, such as needed for medical nebulizer applications. The uni-body foam housing is formed by molding the housing around a pump assembly having special features designed to shield and space apart moving or sensitive internal components of the pump assembly from the foam during the insert molding process. The alternate two-part foam housing is assembled using a union ring having multiple barbed pins that fit into openings in mating faces of the two housing sections.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims benefit to U.S. Provisional Patent Application No. 60/583,424, filed on Jun. 28, 2004.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates to pumps and compressors and in particular to pumps and compressors with low noise characteristics, especially suited for use in medical nebulizer applications.

Nebulizers are commonly used to deliver medication to persons with respiratory ailments. For example, bronchodialators, which are used to open airway passages, are commonly administered with nebulizers. A nebulizer changes liquid medication into a fine, atomized mist or vapor. The medicinal vapor is inhaled through a mouthpiece or mask and the atomized medication is able to penetrate deeply into one's airways because of its fine particle size. The liquid medicine is atomized by mixing it with compressed air or oxygen.

Typical nebulizers include a small compressor with a piston that reciprocates rapidly within a cylinder to pressurize the air. U.S. Pat. No. 6,135,144, assigned to the assignee of the present invention and hereby incorporated by reference as though fully set forth herein, discloses a compressor with a wobble piston. The piston is connected by a connecting rod to an eccentric mounted to a rotating shaft so that its head pivots as it slides within the cylinder. The pressurized air is forced out of the cylinder through a valve head and exhaust chamber to a hose leading to a mixing chamber. Internal conduit is usually necessary to direct the pressurized air leaving the valve head to the outlet port of the housing. After leaving the compressor, the pressurized air passes over an orifice leading from the liquid medicine to aspirate and atomize the medicine, which is then ordinarily mixed with ambient air, oxygen or oxygen enriched air for inhalation.

Persons with significant respiratory problems often require multiple nebulizer treatments every day, each taking several minutes to administer. It is also not uncommon for such persons to receive nebulizer treatments in hospitals, at work or other public places. It is thus important for the nebulizer compressors to operate discreetly. Quiet operation of the compressor can be obtained by insulating the housing, however, this adds bulk and can cause cooling problems. Mufflers can be added at the compressor exhaust, however, this adds hardware and cost.

Conventional metal housings are prone to vibrate in response to the reciprocating components during operation of the pump at an audible frequency that may be too loud for suitable for hospital and home use. To avoid this, various vibration damping spring arrangements have been devised. For example, spring arrangements can be provided to isolate the moving components from the housing to dampen vibration and noise. However, this adds parts and complicates assembly, thereby increasing unit costs.

SUMMARY OF THE INVENTION

The present invention provides a pump, particularly designed for use with a medical nebulizer having improved noise, vibration and manufacturing characteristics.

Specifically, the present invention provides a piston pump having a cylinder and piston disposed along a piston axis and a valve head having an intake port and an exhaust port in communication with the cylinder and respective inlet and outlet ports of a housing. The housing, forming an internal chamber containing the cylinder, piston and valve head, is of molded foam construction. In an especially preferred form, the foam is self-skinning so that the foam has a smooth, generally non-porous outer surface.

In one preferred form, the housing is of uni-body construction. The pump is formed by inserting a pre-assembled pump assembly, including the cylinder and piston arrangement and valve head into a mold die and then molding a uni-body foam housing around this assembly. The pump assembly has special components designed to encapsulate and protect internal components during the insert molding process and provide the internal air space necessary for the drive components to reciprocate after the housing is formed. Preferably, the foam is allowed to cure and develop on its own a skin layer. Inlet and outlet passages are also molded into the housing in communication with the respective intake and exhaust ports of the valve head as are vent passages and a unitary carrying handle. Assembly is completed by attaching a power switch and lead to the actuator, which may be an electromagnet wire coil moving an armature linearly or a motor rotatably driving the piston to reciprocate.

Another preferred form of the pump has a split housing with two similar housing sections that are coupled together by a double sided plastic union ring mated to peripheral faces of the two housing sections by a pin and slot connection. Preferably, the union ring has two sets of tapered barbed pins extending from opposite sides that fit into two sets of openings in the peripheral faces of the two housing sections. The union ring in part defines the inlet of the housing as well as a handle opening aligned with handle openings defined by the housing sections.

The present invention thus provides a compact piston pump having a foam housing providing very low operating vibration and noise such that it is particularly suitable for use in a medical nebulizer device. The pump can have a uni-body construction in which the pump components are pre-assembled and insert molded with the foam forming the housing. Or, the pump can have a split housing in which the parts are assembled with a special ring providing a simple pin and socket connection. Further, the reciprocating drive components of the pump assembly can be suspended in the housing by individual springs or spring stacks to further isolate the housing from vibration caused by the reciprocating elements of the assembly, and thereby reduce noise. The integral air inlet and outlet ports simplify assembly and cost by eliminating the need for separate air lines or tubing.

These and other advantages of the invention will be apparent from the detailed description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a pump having a foam housing according to the present invention;

FIG. 2 is side plan view thereof;

FIG. 3 is an end plan view thereof;

FIG. 4 is an opposite end plan view thereof;

FIG. 5 is a perspective view thereof with the housing shown exploded;

FIG. 6 is another perspective view thereof with the housing shown exploded;

FIG. 7 is a fully exploded perspective view thereof;

FIG. 8 is a side cross-sectional view taken along line 8-8 of FIG. 4;

FIG. 9 is a top cross-sectional view taken along line 9-9 of FIG. 2;

FIG. 10 is another top cross-sectional view taken along line 10-10 of FIG. 2;

FIG. 11 is an end cross-sectional view taken along line 11-11 of FIG. 8;

FIG. 12 is perspective view of alternate embodiment of the pump according to the present invention having a one-piece or uni-body foam housing;

FIG. 13 is a side plan view thereof;

FIG. 14 is a perspective view thereof with the pump assembly shown exploded from the uni-body housing;

FIG. 15 is a fully exploded perspective view thereof;

FIG. 16 is a side cross-sectional view taken along line 16-16 of FIG. 19;

FIG. 17 is a bottom cross-sectional view taken along line 17-17 of FIG. 16;

FIG. 18 is an end view cross-sectional view taken along line 18-18 of FIG. 13; and

FIG. 19 is another end cross-sectional view taken along line 19-19 of FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a pump with a foam housing construction providing quiet operation such that the pump is suitably used in a medical nebulizer application. The foam housing gives the pump improved noise and vibration dampening characteristics in a compact, preferably hand-held, package. These characteristics of the foam housing reduce dependency on other vibration dampening components, such as suspension spring assemblies disposed between the reciprocating components and the housing or isolation springs supporting the fixed components in the housing.

The pump of the present invention will be described herein in two different embodiments. A first embodiment, shown in FIGS. 1-11, has a two-piece foam housing in which the two parts are joined by union ring with multiple pin elements that engage the housing parts. A second embodiment, shown in FIGS. 12-19, has a uni-body foam housing formed around the components of the pump assembly, preferably by an insert molding process. The pump is shown and described herein as an axial (or linear) piston pump. However, other types of pump arrangements are included within the scope of the invention, including rotary driven piston pumps such as wobble type piston pumps.

Referring to FIGS. 1-7, the pump 10 has a compact, generally oblong foam housing 12. The foam can be any moldable or thermoformable foam material, however, the foam is preferably an expanded polyurethane self-skinning foam in which a smooth “skin” forms at the exterior surface of the pump housing 12 as the foam cures so that it is generally non-porous. The foam material is lightweight but strong so as to resist damage or cracking. Importantly, the foam has very good sound insulating and vibration dampening properties.

The foam housing 12 has two shell parts 14 and 16. The shells 14 and 16 are generally the same, each has a peripheral wall 18 with openings 20 spaced there along. Each has two feet 22 and forms a handle opening 24 and vent passages 26. When joined, the shells 14 and 16 define a handle 28 at the top of the housing 12 adjacent the opening 24 and also define an inner cavity 30, an intake passageway 32 and an opening 34 for a power switch 35. Shell 14 is formed with a side opening 36 for an exhaust nipple 38, as discussed below.

The housing shells 14 and 16 are joined by a union ring 40 having a wall 42 disposed between the peripheral walls 18 with a number of barbed pin elements 44 projected toward opposite sides thereof to fit into the openings 20 in the shells 14 and 16, thereby providing a mechanical, pin and socket connection of the two shells 14 and 16. The pins 44 can be formed as a unitary part of the union ring 40 or than can be separate components that fit into associated openings of the union ring 40. A flange 46 extends around the wall 42 to overlap the edges of the shells 14 and 16. The union ring 40 is also formed with an interior wall 48 defining a handle opening 50 aligned with the handle openings 24 in the shells 14 and 16 as well as a port 52 disposed in the intake passageway 32 and an opening 54 disposed in the switch opening 34. The union ring 40 is preferably made of a suitable moldable plastic, such as nylon, ABS, or polystyrene, having sufficient resiliency so that the wall 42 and flange 46 seal against the shells 14 and 16 and form an air tight connection.

Referring now to FIGS. 5, 6 and 8, a pump assembly 56 is contained within the inner cavity 30 of the housing 12. The pump assembly 56 generally includes an electromagnet 58, a piston 60, a cylinder 62 and a valve head 64, all aligned concentrically about a piston axis 66.

Working from left to right in FIG. 8 and right to left in FIGS. 7, 9 and 10, a tail piece 68 having an enlarged trailing end mounts to an axially extending hub 70 of an armature 72. The armature 72 has a series of axial bores 74 (see FIG. 11) therethrough spaced about the axis 66. The armature 72 slides in and out of an annular cavity 76 of a stator 78 which holds a bobbin 80 about which is wound a wire coil 82, thereby comprising the electromagnet 58 when energized by an input current. A diode 83 (shown in FIG. 9) is electrically coupled to the coil 82 to rectify the alternating current input signal so that it drives the armature 72 in only one direction, preferably toward the stator 78.

The armature hub 70 has a bore receiving a narrowed threaded end of a connecting rod 84 to which the tail piece 68 threads to clamp the armature 72 between the tail piece 68 and the connecting rod 84. Clamped between the armature hub 70 and the tail piece 68 is a center portion of one or more leaf springs 86 having their outer peripheries held fixed with respect to the housing 12 by being clamped between a retainer ring 88 and a spacer 90. The connecting rod 84 extends along the piston axis 66 through the center of the armature 72 and the stator 78 to another narrowed threaded end that threads into a bore in a stem of the piston 60, which has an enlarged head 92 to which a piston seal or cup 94 is clamped by a cup retainer 96. The piston cup 94 creates a sliding seal against the inner diameter of the cylinder 62 which is mounted between the valve head 64 and another spacer 98. The spacer 98 is fixedly mounted in the housing 12 to clamp the outer periphery of another one or more leaf springs 100 between it and another retainer ring 102, which is notched to abut and capture the outer edge of the stator 78. The center of the spring(s) 100 are clamped between the connecting rod 84 and the piston stem. The cup retainer 96 is secured by a screw threaded into the connecting rod 84 through the bore of the piston stem. The leaf springs 86 and 100 preferably are configured with a pair of concentric circular rings joined by three spokes. The outer ring preferably includes hair pin elements disposed between the spokes.

The valve head 64 is clamped against one open end of the cylinder 62. The valve head 64 includes a valve plate 103, a chamber housing 104 and a cover 106. The valve plate 103 includes intake 108 and exhaust 110 ports over which are mounted flapper valves (not shown) to control flow through the ports. The intake flapper valve is mounted to the valve plate 103 at the interior of the cylinder 62 and the exhaust flapper valve is mounted at the opposite side of the valve plate 102. The chamber housing 104 is clamped between the valve plate 103 and the cover 106, with a seal 107 therebetween, to define intake 112 and exhaust 114 chambers isolated from each other by a partition wall 116. The exhaust chamber 114 is communication with the exhaust nipple 38 through an opening in the side of the chamber housing 104. The intake chamber 112 is in communication with an intake port 118 in the cover 106 and the intake passageway 32 in the housing 12 leading to ambient via port 52. Suitable o-rings or other gaskets, like seal 107, can be disposed between the components of the valve head 64 and/or between the ends of the cylinder 62 and the mating components as necessary to ensure an air tight seal.

During operation, energizing the coil 82 creates a magnetic flux that drives the armature 72 toward the stator 78, which in turn drives the piston 60 to reciprocate within the cylinder 62. In one preferred version of the pump 10, the piston stroke length is approximately 9 mm (4.5 mm in each direction) and is positioned approximately 1 mm from the top of the cylinder 62 when at top dead center (furthest right in FIG. 9). The piston 60 and the armature 72 reciprocate (along with the tail piece 68 and the connecting rod 84) against the internal spring forces of the springs 86 and 100 arising from the centers of the springs reciprocating with the piston 60 and armature 72.

The reciprocating piston 60 and armature 72 causes the assembly inside the housing 12 to vibrate. The associated noise and movement is dampened by the spring 86 and 100. The number and size of leaf springs is primarily a function of the mass of the piston and the power input frequency. The springs are selected so that in combination (between the two sets) they result in a resonant frequency of the piston and springs (i.e., the spring-mass system) approximately equal to the input frequency, that is 50 or 60 Hertz. For example, in one preferred embodiment there is one spring (or possibly two) at this location and a stack of two springs (or possibly three) at the piston in a 115 v/60 Hz application. A stack of two springs are preferably at each location for a 230 v/50 Hz application. Operating at the resonant frequency improves efficiency and reduces vibration, and thereby reduces noise.

FIGS. 12-19 show an alternate embodiment of the pump in which the foam housing has a uni-body construction. Components of this embodiment that are similar to the above-described embodiment are referred to with similar reference numerals albeit with the suffix “A”.

Referring to FIGS. 12-14, the pump 10A has a compact, generally oblong foam housing 12A. Like in the preceding embodiment, the foam is preferably an expanded polyurethane self-skinning foam in which a smooth, non-porous “skin” forms at the exterior surface. Here, the housing 12A has a uni-body construction such that the components of the pump assembly need to be pre-assembled and inserted into the mold before the housing 12A is formed. The housing 12A is formed with a handle 28A at the top and four feet 22A at the bottom. Vent passages 26A are also formed into the side of the housing 12A as are intake passageway 32A, an opening 34A for an on/off switch 35A and an opening 36A for an exhaust nipple 38A. The vent passages 26A, intake passageway 32A, switch opening 34A and exhaust opening 38A can be formed during the molding process or by a machining operation thereafter.

Referring now to FIGS. 14 and 15, a pump assembly 56A is contained within the inside of the housing 12A and generally includes an electromagnet 58A, a piston 60A, a cylinder 62A and a valve head 64A, all aligned concentrically about a piston axis 66A.

With reference to FIGS. 15-19 and working from left to right in FIG. 15 and right to left in FIGS. 16 and 17, the pump assembly 56A includes a dome-shaped end cap 202 defining an interior space for movement of the piston 60A and an armature 72A. The end cap 202 has openings in communication with associated vent openings 26A allowing ambient conditions to exist therein and prevent back pressure piston. This piece is necessary here because of the uni-body construction of this embodiment and the fact that the pump assembly 56A is inserted molded within the housing 12A, without it the foam would adhere to, or at least form tightly around, the pump assembly 56A so as to prevent reciprocation of the otherwise movable components. The end cap 202 has a section defining an open cavity 203 for the power switch 35A. The end cap 202 has an annular flange at its periphery that is notched to receive the periphery of an annular spacer 90A between which is clamped one or more leaf springs 86A (one shown). The spacer 90A abuts the periphery of a stator 78A, which defines a cavity 76A (see FIG. 16) in which is disposed a bobbin 80A about which is wound a wire coil 82A, thereby providing the electromagnet 58A when energized by an input current. As before, a diode 83A, shown in FIG. 17, is electrically coupled to the coil 82A to rectify the alternating current input signal so that it drives the armature 72A in only one direction, preferably toward the stator 78A. Also as before, the armature 72A has a series of axial bores 74A therethrough and slides in and out of part of the annular cavity 76A of the stator 78A.

The armature 72A has a central hub 70A with a bore through which extends a bolt 204 passing through a connecting rod 84A and threading into the stem of the piston 60A. Clamped between the armature hub 70A and a head of the bolt 204 is a center portion of the one or more leaf springs 86A (one shown in FIG. 15), configured as described above, which have their outer peripheries held fixed with respect to the housing 12A. The connecting rod 84A extends along the piston axis 66A through the center of the stator 78A and abuts the stem of the piston 60A, which as before has an enlarged head 92A to which a piston seal or cup 94A is clamped by a cup retainer 96A. Clamped between the piston 60A and the connecting rod 84A are the center portions of one or more leaf springs 100A (two shown in FIG. 15), which have their outer peripheries clamped between a retainer ring 102A and an annular electromagnet cup or housing 206, which surrounds the stator 78A and armature 72A and has a recess at one end in which one end of the cylinder 62A is disposed. The other end of the cylinder 62A fits into a groove in a valve plate 103A, which in this case takes a cup shape having an annular wall 208 spaced from and surrounding the cylinder 62A and abutting the electromagnet cup 206.

The valve plate 103A and the electromagnet cup 206 have the cup-like configuration to enclose the components therein to shield and space them from the foam during the molding of the housing, as is the purpose of the end cap 202. Both the valve plate 103A and the electromagnet cup 206 also have openings that are communication with the housing vents 26A to allow cooling air flow therethrough as well as to allow these non-compression or vacuum areas of the pump assembly to operate at ambient pressure.

The valve head 64A includes the valve plate 103A, a chamber housing 104A and a cover 106A. The valve plate 103A includes intake 108A and exhaust 110A ports over which are mounted flapper valves (not shown) to control flow through the ports. The intake flapper valve is mounted to the valve plate 103A at the interior of the cylinder 62A and the exhaust flapper valve is mounted at the opposite side of the valve plate 103A. The chamber housing 104A is clamped between the valve plate 103 a and the cover 106A to define intake 112A and exhaust 114A chambers isolated from each other by a partition wall 116A. The exhaust chamber 114A is communication with the exhaust nipple 38A through an opening in the side of the chamber section 104A. The intake chamber 112A is in communication with an intake port 118A in the cover 106A and the intake passageway 32A in the housing 12A leading to ambient air. Like above suitable o-rings or other gaskets can be disposed between the components of the valve head 64A and/or between the ends of the cylinder 62A and the mating components as necessary to ensure an air tight seal.

As mentioned, given the uni-body construction of this embodiment of the pump, a special insert molded assembly method is utilized. In particular, the aforementioned components of the pump assembly 56A are pre-assembled and inserted into a mold die. The foam resin is then, preferably injected, into the die to form the housing 12A around the pump assembly 56A. A non-porous skin forms at the exterior of the foam as it cools, preferably while the housing 12A is still inside the mold. As mentioned, preferably the vent and intake and exhaust openings are formed by the molding process to be in communication with the respective intake and exhaust ports of the valve head 64A. Similarly, the vent passages and handle are also preferably so formed. The power on/off switch 35A, with leads (not shown) connecting it to the electromagnet wire coil, is mounted to the housing 12A at the switch opening 200. The switch opening 200 is located to allow access to the coil 82A for coupling the electrical leads thereto.

The present invention thus provides a compact axial piston pump having a foam housing providing very low operating vibration and noise such that is particularly suitable for use in a medical nebulizer device. The pump can have a uni-body construction in which the pump components are pre-assembled inserted molded with the foam forming the housing. Or, the pump can have a split housing in which the parts are assembled with a special ring providing a simple pin and socket connection. Further, the drive assembly can be suspended in the housing by spring stacks to further isolate the housing from vibration caused by the reciprocating elements of the assembly, and thereby reduce noise. The integral air inlet and outlet ports simplifies assembly and cost by eliminating the need for separate air lines or tubing.

Illustrative embodiments of the present invention have been described above in detail. However, the invention should not be limited to the described embodiments. For example, it is within the scope of the invention to substitute other spring members for the leaf springs described above, such as compression springs or other energy absorbing members made of suitably resilient materials, such as rubber or foam. To ascertain the full scope of the invention, the following claims should be referenced. 

1. A pump having a cylinder and piston disposed along a piston axis, the piston being driven to reciprocate within the cylinder along the piston axis and pass air through a valve head having an intake port and an exhaust port in communication with the cylinder and respective inlet and outlet ports of a housing being of molded foam construction and forming an internal cavity containing the cylinder and piston.
 2. The pump of claim 1, wherein the foam is self-skinning.
 3. The pump of claim 1, wherein the housing is of uni-body construction.
 4. The pump of claim 3, wherein the housing defines a handle.
 5. The pump of claim 1, wherein the housing includes first and second housing sections.
 6. The pump of claim 1, wherein the first and second housing sections have peripheral faces and are coupled together by a double sided union ring mated to the peripheral faces.
 7. The pump of claim 6, wherein the union ring is plastic.
 8. The pump of claim 6, wherein union ring is mated to the peripheral faces by pin and slot connections.
 9. The pump of claim 8, wherein the union ring has a first set of pins extending from one side and a second set of pins extending in an opposite direction from the first set from an opposite side such that the first set of pins is disposed in an associated plurality of openings in the peripheral face of the first housing section and the second set of pins is disposed in an associated plurality of openings in the peripheral face of the second housing section.
 10. The pump of claim 9, wherein the first and second set of pins have tapered locking barbs.
 11. The pump of claim 6, wherein the union ring in part defines the inlet of the housing.
 12. The pump of claim 6, wherein the peripheral faces of the first and second housing sections define a handle opening and wherein the union ring defines a handle opening aligned with the handle openings of the first and second housing sections.
 13. The pump of claim 1, wherein the housing includes a plurality of vent passages venting the internal cavity to ambient.
 14. The pump of claim 1, wherein the piston is driven by an armature of an electromagnet mounted within the housing by one or more springs.
 15. The pump of claim 14, wherein the electromagnet is contained within an electromagnet housing inside of the internal cavity of the housing.
 16. The pump of claim 15, wherein the electromagnet housing includes an opening in communication with a vent in the housing.
 17. The pump of claim 15, wherein the electromagnet housing has an open end that is closed by an end cap which defines an air volume in which a reciprocating component can move along the piston axis.
 18. The pump of claim 17, wherein the end cap is dome-shaped and has an opening in communication with a vent in the housing.
 19. The pump of claim 1, wherein the valve head includes a valve plate with an annular wall defining an air volume in which the cylinder is disposed.
 20. The pump of claim 1, wherein the annular wall has an opening in communication with a vent in the housing.
 21. A method of making a pump having a pump assembly including a cylinder and piston arrangement and a valve head having an intake port and an exhaust port in communication with the cylinder, the method comprising the steps of: pre-assembling the pump assembly; inserting the pump assembly into a mold die; and molding a foam housing around the pump assembly.
 22. The method of claim 21, further including the step of allowing the foam cure and form a skin.
 23. The method of claim 21, further including the step of forming inlet and outlet passages in the housing in communication with the respective intake and exhaust ports of the valve head.
 24. The method of claim 21, further including the step of forming one or more vents in the housing.
 25. The method of claim 21, further including the step of forming a handle unitary with the housing.
 26. The method of claim 21, further including the step of coupling a power switch and lead to the electromagnet wire coil.
 27. The method of claim 21, wherein an electromagnet is contained within an electromagnet housing inside of the internal cavity of the housing.
 28. The method of claim 27, wherein the electromagnet housing includes an opening in communication with a vent in the housing.
 29. The method of claim 28, wherein the electromagnet housing has an open end that is closed by an end cap which defines an air volume in which a reciprocating component can move along the piston axis.
 30. The method of claim 29, wherein the end cap is dome-shaped and has an opening in communication with a vent in the housing.
 31. The method of claim 21, wherein the valve head includes a valve plate with an annular wall defining an air volume in which the cylinder is disposed.
 32. The method of claim 31, wherein the annular wall has an opening in communication with a vent in the housing. 